To construct and provide a convenient and fast information transmission environment, telecom service providers constantly develop and ameliorate existing mobile communication network techniques, for example, the currently widely used universal mobile telecommunications system (UMTS) of 3rd generation (3G) mobile communication technology, UMTS terrestrial radio access network (UTRAN), GERAN (GSM/EDGE) system, worldwide interoperability for microwave access (WiMAX) system and other wireless network techniques are simultaneously developed and ameliorated.
In many mobile communication networks, a base station (BS) is generally used as a communication accessing point for a plurality of wireless communication devices. Wherein, the wireless communication device can be a mobile station (MS) (for example, a mobile phone) or a user equipment (UE) (for example, a notebook computer), etc. Certainly, the MS can also be the UE, and vice versa. The wireless communication device can be an immobile device (for example, a personal computer (PC)) or a mobile device (for example, a cellular phone, a laptop computer or other mobile communication devices). Moreover, recent network developments of the mobile communication network all focus on ameliorating an effect of wireless broadband access (WBA). Since a coverage range (which is also referred to as a macro coverage area) of a macro BS is wide, the supported mobile communications devices within such coverage range are numerous, so that the macro BS has a relatively heavy burden in communication. The macro BS and the macro coverage area thereof are altogether referred to as a macrocell. Moreover, a difficulty for constructing the macro BS is increased due to factors such as environmental protection and remonstrations, etc., and an indoor communication performance may have communication dead corners due to factors such as a construction location of the macro BS, shielding of the building or other obstacles, etc., so that the indoor communication quality can be uneven. Therefore, construction of a local or a sub-BS (for example, an ultra-micro BS or a Femto BS, or a home BS) is a good solution for increasing the indoor communication performance.
Properties such as low power and high bandwidth of the sub-BS allow a user to install the mobile communication accessing point by himself, and the sub-BS can provide a sub coverage area with a relatively small coverage range. The Femto BS and the sub coverage area thereof are altogether referred to as a femtocell, which can be disposed in a residential district or a small business environment for utilization. A local femtocell can be constructed and added to a part of regions of a macrocell, so as to cope with a requirement of high intensity mobile communication. Moreover, the sub-BS can be connected to a core network through a cable communication access mechanism of a digital subscriber line (DSL), so as to enjoy a broadband mobile communication service. In overall, explanation of the advantages for constructing the sub-BS is twofold. In view of a telecom practitioner, the advantages include (1) a backhaul capacity requirement is reduced; (2) a wireless capacity is increased; (3) loopholes of the coverage range are reduced and new integrated services are provided. In view of a customer, the advantages include (1) a good indoor coverage range and quality is achieved without changing a phone; and (2) one phone-one phone number and regional specific price are achieved.
However, since the coverage areas of the macro BS and the sub-BS are often overlapped, interference is occurred during signal transmission. Moreover, a transmission quality of the macro BS is decreased due to the interference or allocation of resource blocks.